Solid state actuator capable of plating and plating material storage

ABSTRACT

In one embodiment, a solid state actuator is provided which includes a pair of electrodes and a solid state storage material having a plating material. A solid state ion transport material is adjacent the solid state storage material such that the solid state storage material is located between an anode of the pair of electrodes and the solid state ion transport material. The pair of electrodes are connected so as to be capable of providing an actuation voltage across the solid state storage material to provide transport of plating material cations through the solid state ion transport material between the solid state storage material and a cathode electrode of the pair of electrodes.

CROSS REFERENCE TO RELATED APPLICATION

The following application is a divisional of U.S. patent applicationSer. No. 10/927,965, filed Aug. 28, 2004 now U.S. Pat. No. 7,298,017, byLiu et al., entitled ACTUATION USING LITHIUM/METAL ALLOYS AND ACTUATORDEVICE, herein incorporated by reference in its entirety.

BACKGROUND

Solid state actuators are expected to be useful in the aerospace, andspace industries, as well as in certain next generation armed forcesconcepts.

While ferroelectric, ferromagnetic, and twinning based actuators permitrelatively high energy density, each of these actuators shares acritical weakness when considering large deformation. Each of thesemechanisms are essentially volume conserving and occur at constantdensity, limiting deformation to local shifts in crystal structure andtherefore relatively small overall deformation.

Electroactive polymers including, conducting polymers and ionic basedactuation such as Ionic-Polymer-Metal-Composite or IPMC, exploit areversible electrochemical reaction to perform mechanical work. Onedisadvantage of these systems, however, is that they have limited stressoutput. Although conducting polymers yield relatively large strain(˜1-5%), it is at low blocking stress. Macro scale conducting polymeractuators typically have stress output on the order of 1-6 MPa, and bulkenergy density of 10-80 kJ/m³.

Another disadvantage is that they require a liquid or a gel electrolyte.Both the polymeric nature of these materials and the liquid electrolytelimit their applicability to a narrow temperature range. This limits theapplicability of these materials to many environments commonlyencountered in structural applications.

SUMMARY

In some embodiments, a solid state actuator is provided which includes apair of electrodes and a solid state storage material having a platingmaterial. A solid state ion transport material is adjacent the solidstate storage material such that the solid state storage material islocated between an anode of the pair of electrodes and the solid stateion transport material. The pair of electrodes are connected so as to becapable of providing an actuation voltage across the solid state storagematerial to provide transport of plating material cations through thesolid state ion transport material between the solid state storagematerial and a cathode electrode of the pair of electrodes.

In some embodiments, a solid state actuator is provided including a pairof electrodes a solid state storage material having a plating material.A solid state ion transport material is adjacent the solid state storagematerial such that the solid state storage material is located betweenan anode of the pair of electrodes and the solid state ion transportmaterial. A plating layer is between the solid state storage materialand the pair of electrodes. The pair of electrodes are connected so asto be capable of providing an actuation voltage across the solid statestorage material, with the plating material being such that a change involume of the solid state storage material upon removal of the platingmaterial therefrom is less than a change in volume of a plating layerdeposited between the pair of electrodes so as to provide displacementfor the solid state actuator.

In some embodiments, a solid state actuator is provided which includes apair of electrodes and a solid state storage material comprising aplating material. A solid state ion transport material is adjacent thesolid state storage material such that the solid state storage materialis located between an anode of the pair of electrodes and the solidstate ion transport material. A plating layer is between the solid statestorage material and the pair of electrodes. The pair of electrodesbeing connected so as to be capable of providing an actuation voltageacross the solid state storage material, with the plating material beingsuch that a change in volume of the solid state storage material uponremoval of the plating material therefrom is less than a change involume of a plating layer deposited between the pair of electrodes so asto provide displacement for the solid state actuator.

In various embodiments, the plating layer may be formed adjacent acathode electrode of the pair of electrodes.

Additional and further embodiments are also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cut-away side view illustration of a solid state actuationprocess in accordance with the present invention.

FIG. 2 shows a cut-away side view of an actuator embodiment inaccordance with the present invention.

FIG. 3 shows a cross-sectional view of an actuator embodiment having anstacked configuration in accordance with the present invention.

FIG. 4 shows a cross-sectional view of an actuator embodiment having aninterdigitated configuration in accordance with the present invention.

FIG. 5 shows an orthographic illustration of a diced block actuator toform separate elongated actuator structures.

FIG. 6 shows an orthographic illustration of the diced block actuator ofFIG. 5 with the elongated structures separated.

DESCRIPTION Solid State Lithium Ion Actuator FIG. 1

FIG. 1 is a cut-away side view illustration of an actuation processutilizing lithiation of metals in an entirely solid state mechanicalactuator 100. Actuation occurs via a reversible process of lithiuminsertion and removal of lithium ions from a volume changing material110. Once removed from a lithium expanded material 110 a, they arestored in a lithium storage material 130. To maximize actuationdistance, the lithium storage material 130 typically is volumeconserving, or does not change volume to a significant degree ascompared to the volume changing material 110. A lithium ion transportmaterial 120 is located between the volume changing material 110 and thelithium storage material 130. In some embodiments, the combinedmaterials provide an actuator capable of large strain and stress.

A voltage potential V, applied across the actuator via electrodes 140and 150, controls ion transport. The volume changing material 110 formsthe anode of the actuator. The lithium ion transport material 120 is anelectrolyte which is a lithium ion conductor and electron insulator. Thelithium storage material 130 forms the cathode.

For the lithium ion transport material 120, a material which does notalso transport electrons may be used. Although typical electrolytes suchas soft polymers including salt dissolved in polymer, dry polymerelectrolyte, or polymer gel may provide adequate lithium ion transport,for actuation at high temperature and rugged environments, a solidlithium ion conductor material is preferred. Solid state lithium iontransport materials have a mechanical performance that allows largemechanical loads to be supported.

One potential drawback with some solid lithium ion conductor materialsis that they can suffer from poor electrochemical stability above athreshold, i.e. in a window of over 4 V. If this is the case, thecathode-anode pairs can be selected so that the device may be operatedat voltages within a range that is below the stability threshold for theselected transport material. By appropriately selecting the operatingrange, additional types of solid lithium ion conductors may be utilizedwith improved stability.

In one possible embodiment, the solid lithium ion conductor may be asuper ionic conductor such as lithium sulfide, for exampleLi_(4−x)Ge_(1−x)P_(x)S₄ (0.4<x<0.8). It is a high stiffness materialthat exhibits acceptable lithium ion transport at room temperature, andexcellent transport at elevated temperatures as low as 100°. In theabove example the phosphate can be replaced with nitrogen or the like,and/or the germanium may be replaced with silicon or the like.

High stiffness lithium ion conductor materials are well suited for usein actuators. High stiffness materials include ceramics and othercrystal lattice material, as well as some strong amorphous materials.Some amorphous materials, such as vacuum deposited amorphous materials,are high stiffness as they have sufficient strength to supportactuation. Typically high stiffness materials exhibit stress output ofabout 50 Gpa or more. Most inorganic lithium ion conductors are highstiffness. Many high stiffness ion conductors are possible, for example:super ionic conductors, such as, lithium sulfide, LiSICON, Thio-LiSICON;doped lithium materials such as nitrogen doped lithium phosphate orLi—N—P—O, zirconium doped lithium silicate or Li—Si—Zr—O, Li—B—O,Li—B—O—I, Li—Si—P—O, Li—Nb—P—O, Li—B—S, Li—La—Ti—O, Li—Ti—Al—P—O,Li—Si—Al—O, etc.; or other materials known in the lithium ion batteryfield.

It is significant to note that in an actuator, ion conductor materialwhich allows leakage current is acceptable in certain embodiments, ascharge conservation is not always paramount in actuator implementations.For example, Thio-LiSICON contains sulfur which can allow chargeleakage. Nevertheless, it may be utilized in certain actuatorembodiments due to its strong material properties.

The lithium storage material 130 preferably is formed of a material thatdoes not show large changes in volume. The lithium storage material 130may be formed of: carbonaceous materials such as graphite; transitionmetal oxides such as lithium titanium oxide, lithium manganese oxide,lithium cobalt oxide, lithium nickel oxide, etc.; lithium metalphosphates such as lithium iron phosphate, lithium vanadium phosphate,lithium manganese phosphate, lithium cobalt phosphate, etc.; or othermaterials known in the lithium ion battery field.

In one embodiment, the lithium storage material may be composed ofgraphite, which can store large amounts of lithium while exhibiting onlysmall expansion/contraction. In one embodiment, the lithium storagematerial 130 is composed of lithium titanium oxide, such asLi_(4+x)Ti₅O₁₂, where x is 0-3. Lithium titanate is a ceramic material,with high stiffness, which can store large amounts of lithium, and alsodoes not significantly change in volume. Other types of lithiumcontaining compounds which can reversibly accept and release lithiumwithout experiencing significant volume change during the process arepossible. Moreover, the lithium storage material may include solidinorganic compounds that have polymer lithium conducting mediums oradditives.

Volume changing material 110 opposing the lithium storage material 130across the ion transport material 120. The volume changing material 110is primarily responsible for the actuation distance of the actuator 100.

In some actuator embodiments, it is desirable to have a robust volumechanging material 110, one that is capable of reliably providing largeactuation distances while supporting high stress and strain. Ofparticular concern in actuators, is that the large expansion of thevolume changing material 110, combined with the applied stress andstrain of the actuator, could lead to mechanical failure (i.e.crumbling) of the volume changing material 110. Another concern is thatcharge capacity (and volume expansion) could decrease precipitouslyduring only a few cycles for pure volume changing materials, such as Sn.Several techniques may be utilized to provide more repeatable lithiuminsertion/removal in actuators. In some implementations of the presentinvention, improved repeatability may be achieved by alloying thelithium accepting materials with other non-active materials, bycontrolling the applied voltage closely so that transition occurs onlybetween two more closely related compounds, and/or by changing the sizescale of the lithium accepting metal.

In actuator embodiments which require repeated cycles of lithiuminsertion and removal under high stress and strain, alloys may beutilized to provide improved repeatability of the volume changingmaterial 110. Various alloyed metals, for example alloys of Sn, Sb, andAg, yield a volume changing material 110 that will exhibit morerepeatable cycles than the pure elements. Sn alloys in particular, suchas for example SnSb, provide highly repeatable reactions with lithium,and allow control of strain output by varying the molar fraction of eachcomponent. Other alloys are possible, such as alloys of Al, Si, Mg, Fe,Ti, Cu, Ni, or the like.

Improved repeatability of the volume changing material 110 also may beobtained by mechanically mixing fine powders of lithium acceptor alloys.Encapsulation of an active lithium accepting metal by a non-active metalmay help accommodate the volume expansion while maintaining electricalcontact. In an alternate embodiment, a volume changing material 110which includes several oxides containing lithium reactive metals arecombined to make a glassy material that is further processed to createbound powder. Each of these implementations utilizes a compositematerial with randomly distributed active components in a lithiumconducting medium. As discussed further below, heterogeneous mixturesmay be utilized in certain embodiments to provide anisotropic expansionof the volume changing material.

In some implementations, careful control of the applied voltage limitsmay be utilized to provide more repeatable dimensional changes. Becausethe lithiation of metal species is tremendously sensitive to appliedvoltage, controlling the lithiation of volume changing material limitsthe reaction to compounds of more compatible dimensions. By selectingthe appropriate actuation voltage limits, control of species formationmay be obtained to improve the cyclic stability of the device. Thevoltage source may have associated therewith, a processor or equivalenthardware and/or software means, to control the actuation voltage withinan operating range below a stability threshold voltage for the solidstate lithium ion transport material so as to inhibit mechanical failureof the solid state lithium ion transport material.

The cyclical stability gain achieved by limiting the voltage range mayresult from inhibiting of the formation of highly strain incompatible Licompounds that cause excessive fracture and localized failure. This ispossible in some actuator embodiments because the voltage and the chargedensity typically are not primary concerns in most embodiments of theactuator. Instead, the cyclical stability of the dimensional change andblocking stress is of greater concern. So, limiting the voltage range toimprove stability is possible in certain implementations.

In some embodiments, the volume changing material 110 is made of activeparticles. Minimizing the size of the particles from 50 microns to 1micron improves the cyclic stability, reducing the rate of fractures.Alloys and mixtures of solid thin film volume changing materials is alsopossible. At smaller geometries it is likely that improved cyclicalstability is a result of a decrease in the defect density at smallerscale, a reduction in diffusion length and corresponding reduction instrain gradient, and/or a difference in the absolute expansiondimension.

As such, the insertion/removal reaction, for example between of Sn andLi, can be controlled and modified by changing the size of thecomponents, varying the architecture of the alloy, and employingheterogeneous mixture concepts, as well as by controlling of the appliedvoltage to determine which species are principally formed during thereaction. These techniques may be utilized so as to tailor the reactionto enhance the performance of the material for actuator applications.

Additional Actuator Embodiments FIGS. 2-6

The process of lithiation of metals causes isotropic volume expansion.In some implementations, however, it is desirable to have the movementof the actuator provided mainly in a direction of work, and limited inother (lateral) directions.

FIG. 2 shows a cut-away side view of an alternate actuator embodiment inaccordance with the present invention. In certain embodiments, thevolume changing material 210 may include an active component 212embedded in a matrix 214. In the embodiment shown, the active component212 is comprised of particles which are aligned generally along vectorsextending in the direction of work for the actuator 200. The activecomponent particles 212 may be aligned electrostatically ormagnetically. The active particles 212 change their volume in responseto the reversible process of lithium insertion and removal of lithiumions from the active particles 212.

The matrix 214 may be a non-active matrix composed of a compliantmaterial which allows transport of lithium ions to the active particles212. In some embodiments, the non-active matrix 214 may be acomposition, such as for example poly ethylene oxide and lithium salt.

The active component particles 212 are aligned along vectors so thatwhen the particles expand they cause expansion of the actuator mainly inthe direction of work. Alignment of the active component particles 212creates a different mechanical connectivity in the alignment direction,than in orthogonal directions. If each active component particle expandsisotropically, the composite material 210 expansion will be greater inthe direction of the alignment as the stress fields associated with thisexpansion will add constructively. In orthogonal directions, the stressfields of separate particles do not interact, and the cumulativeexpansion is reduced. Therefore this arrangement of active componentparticles 212 and matrix material 214 produces anisotropic expansion.

As there is substantially more expansion along a vector in the directionof work, the expansion of the particles 212 along a vector sums toprovide volume expansion in the direction of the vector. Thus, thevolume expanding material composite 210 provides motion mainly in thedirection of work, while lateral motion may be significantly reduced.

The active component particles 212 may be regular, or irregular. Theparticles 212 may be elongated particles, such as fibers, rods, tubes,blocks, ribbons, or the like. The elongated particles may be arranged ina stacked configuration in the non-active matrix so that they arealigned along the direction of work. With elongated particles, there isa greater distance of expansion along their length, so the expansiondistance of the volume expanding material composite 210 in the elongateddirection (along in the direction of work) is greater. Thus, althoughthe active material particles 212 expand and contract isotropically, thenon-active matrix moves mainly in the direction of work.

Similar to above, a voltage potential V (not shown in FIG. 2) connectedacross the actuator 200 via electrodes 140 and 150 controls iontransport between the lithium storage material 130 and the volumeexpanding material 210, through the lithium ion transport material 120.The volume expanding material 210 expands in response to lithiation ofthe active component particles 212.

FIG. 3 shows a cross-sectional view of an actuator embodiment 300 havingan stacked configuration. The speed of an actuator is controlled in partby the distance that the lithium ions travel through the actuator. Toincrease actuation displacement without impacting actuator speed,multiple actuators 200, may be stacked to cumulate the actuationdistance. With the stacked arrangement, since the distance that thelithium ions travel within their respective actuator 200 does notchange, the actuation time does not increase.

FIG. 4 shows a cross-sectional view of an actuator embodiment 400 havingan interdigitated configuration. The mechanical properties of theactuator 400 may be enhanced by configuring the actuator 400 in aninterdigitated arrangement. In this embodiment, portions of volumeexpanding material 410 a, 410 b, and 410 c are recessed within thelithium storage material 430. The lithium ion transport material 420 islocated between the lithium storage material 430 and the portions ofvolume expanding material 410 a, 410 b and 410 c. A voltage potential isapplied across the actuator 400 via electrodes 440 and 450. The portionsof volume expanding material 410 a, 410 b, and 410 c are surrounded onat least three sides by the lithium storage material 430. As such, theportions of volume expanding material 410 a, 410 b, and 410 c willexpand to extend out of the lithium storage material 430.

It is also significant to note that recessing the volume expandingmaterial 410 within the lithium storage material 430 increases theamount of lithium storage material 430 opposing the volume expandingmaterial 410. This facilitates ion diffusion. In some embodiments, thisconfiguration can reduce ion diffusion lengths to increase actuationspeed.

FIG. 5 shows an orthographic view of a block actuator 510. The blockactuator may be machined, or diced, or otherwise subdivided to formelongated structures 510 a-510 l, as shown in FIG. 6. The elongatedstructures 510 a-510 l may be blocks, rods, posts, pillars, or otherelongated solid. As shown in FIG. 6, the elongated structures 510 a-510lb may be arranged in a pillared configuration, separated so that theirlateral expansion does not cumulate, or does not transfer laterally.Compliant material may be added to fill the gaps between the elongatedstructures 510 a-510 l to “absorb” the lateral expansion of the volumeexpanding material of the elongated structures 510 a-510 l.

In some embodiments, it is not necessary that the elongated structures510 a-510 l be totally isolated structures to limit the lateralexpansion by the volume changing material of the elongated structures510 a-510 l. Forming channels in the volume changing material of theblock 510, or segmenting the volume changing material of the block 510,may be utilized to limit lateral expansion. Thus, in some embodimentsthe pillared configuration extends only through volume changingmaterial.

An important advantage of electrochemical actuation is that chargetransfer controls strain generation, and therefore, actuation iscontrolled by the applied voltage rather than the applied field. Thevoltage necessary to drive the reaction depends only on the relativepotential of the electrodes, and thus can be limited to a few voltsthrough careful selection of electrode materials. Typically they haverelatively large induced deformation, relatively light weight, andscalability down to small geometries.

Metals such as tin, antimony, and aluminum absorb large fractions oflithium ions resulting in a huge volume expansion of 10-300% or more. Inaddition, lithium based electrochemical actuators have other advantagesas compared to polymer based electrochemical systems. These solid statedevices do not require a liquid electrolyte, and furthermore, due toenhancement of diffusion at higher temperature, actually exhibitincreased power density at elevated temperatures. As such, someembodiments may provide increased energy density, as well orders ofmagnitude larger strain deformation than achievable with currentcomparable materials.

In certain embodiments, high stiffness components may support largeforce output in the megapascal range. These properties combined, mayelevate Li-Metal actuation to energy densities equal to or greater thanthe largest conventional materials, such as NiTi shape memory alloyswhich have >1 MJ/kg energy density. An additional quality furtherseparates these lithium based actuation from currently available solidstate actuators.

As opposed to other actuator means, the lithium removal/insertionprocess is a reversible chemical reaction where volume is not conserved.The total overall volume of the actuator changes. Furthermore, otheractuator means may be limited to relatively low operating temperaturesdue to both the polymeric nature of the materials, and the necessaryliquid or gel electrolyte. Unlike conducting polymers, which canexperience a loss in polymer stiffness at higher temperatures, severalembodiments of the metallic based lithium storage/removal actuatorsmaintain stiffness even at higher temperatures. Moreover, in someembodiments, ionic diffusion is enhanced at higher temperatures, whichleads to higher speed actuation. These properties combined may enablemany active structural applications previously not considered due to thedemands on actuator material, both in terms of mechanical output andenvironmental conditions. As such, certain embodiments may deliver bothlarge strain output and relatively large stress output, even whenoperated in harsh environments. Hence, some embodiments allowsignificantly higher working temperatures. Embodiments composed entirelyof metals and ceramics, could flourish at temperatures from 150-300degrees Celsius, or potentially up to 800 degrees Celsius, where othersare much less effective.

Certain embodiments of the present invention are not limited to lithiumstorage and lithium storage mechanisms, but are applicable to thestorage of other materials that produce a net change in volume. Forexample, sodium storage material, such as sodium tin, may be utilized insome embodiments. Other materials are possible. In general, someembodiments may utilize any combination of materials, where thecombination provides a net change in volume. Referring to FIG. 1, thestorage material 130 provides the cations for transporting through theion transport material 120 between the storage material 130 and thecathode electrode 150. Appropriate storage materials capable ofreleasing cations are selected so that the change in volume of thestorage material 130 is less than the change in volume of the volumechanging material 110, so as to create a net displacement for theactuator 100.

In yet other embodiments, the volume changing material as describedabove may be omitted. In such embodiments, the actuator displacement isachieved by plating of material on the electrode 150. For example inFIG. 1, the layer 110 a would be a plated material layer. The layer 110b could be completely removed, if desired, as the plated material is notalloying with a volume changing material, but instead is creatingdisplacement in an actuator by deposition on, and removal from, thesurface of the electrode 150. To provide actuation displacement,however, the layer 110 b need not be completely removed, but instead maybe a reduced, a partial, or even a residual layer as compared to a moreplated layer 110 a. As such, surface deposition and removal of theplating material 110 a creates the actuator displacement.

The plating material 110 a may be, for example lithium, copper, silver,sodium, potassium, magnesium, or other conductive material. In suchembodiments, the storage material 130 provides plating material cationsfor transporting through the ion transport material 120 between thestorage material 130 and the cathode electrode 150. The storage material130 releases plating cations. The change in volume of the storagematerial 130 is less than the change in volume of the plating materiallayer 110 a to provide displacement for the actuator 100. Possiblematerials for the lithium storage material 130 are discussed above.Other example solid state storage materials are MV₂O₅, where M is Na,Ag, Mg, K, Cu, etc. Thus, surface plating and removal of cations at thecathode electrode is primarily responsible for the actuation distance ofthe actuator 100 in such an embodiment.

Having described this invention in connection with a number ofembodiments, modification will now certainly suggest itself to thoseskilled in the art. As such, the invention is not to be limited to thedisclosed embodiments except as required by the appended claims.

1. A solid state actuator comprising: a) a pair of electrodes; b) asolid state storage material comprising a plating material; c) a solidstate ion transport material adjacent the solid state storage materialsuch that the solid state storage material is located between an anodeof the pair of electrodes and the solid state ion transport material;and d) the pair of electrodes being connected so as to be capable ofproviding an actuation voltage across the solid state storage materialto provide transport of plating material cations through the solid stateion transport material between the solid state storage material and acathode electrode of the pair of electrodes.
 2. The solid state actuatorof claim 1 further comprising a plating layer adjacent the cathodeelectrode.
 3. The solid state actuator of claim 2, wherein the platinglayer comprises at least one of lithium, copper, silver, sodium,potassium, or magnesium.
 4. The solid state actuator of claim 2, whereinthe solid state storage material comprises at least one of a lithiumstorage material or MV₂O₅, where M comprises at least one of Na, Ag, Mg,K or Cu.
 5. The solid state actuator of claim 2, wherein the platingmaterial is a material that is non-alloying with the cathode electrode.6. A solid state actuator comprising: a) a pair of electrodes; b) asolid state storage material comprising a plating material; c) a solidstate ion transport material adjacent the solid state storage materialsuch that the solid state storage material is located between an anodeof the pair of electrodes and the solid state ion transport material;and d) the pair of electrodes being connected so as to be capable ofproviding an actuation voltage across the solid state storage material;and e) a plating layer formed from the plating material upon applicationof an actuation voltage across the pair of electrodes such thatdeposition of and removal of the plating layer causes actuatordisplacement.
 7. The solid state actuator of claim 6 wherein the platinglayer is adjacent a cathode electrode of the pair of electrodes.
 8. Thesolid state actuator of claim 7, wherein the plating layer comprises atleast one of lithium, copper, silver, sodium, potassium, or magnesium.9. The solid state actuator of claim 7, wherein the solid state storagematerial comprises at least one of a lithium storage material or MV₂O₅,where M comprises at least one of Na, Ag, Mg, K or Cu.
 10. The solidstate actuator of claim 7, wherein the plating material is a materialthat is non-alloying with the cathode electrode.
 11. A solid stateactuator comprising: a) a pair of electrodes; b) a solid state storagematerial comprising a plating material; c) a solid state ion transportmaterial adjacent the solid state storage material such that the solidstate storage material is located between an anode of the pair ofelectrodes and the solid state ion transport material; d) a platinglayer between the solid state storage material and the pair ofelectrodes; e) the pair of electrodes being connected so as to becapable of providing an actuation voltage across the solid state storagematerial; and f) the plating material being such that a change in volumeof the solid state storage material upon removal of the plating materialtherefrom is less than a change in volume of a plating layer depositedbetween the pair of electrodes so as to provide displacement for thesolid state actuator.
 12. The solid state actuator of claim 11, whereinthe plating layer is adjacent a cathode electrode of the pair ofelectrodes.
 13. The solid state actuator of claim 12, wherein theplating layer comprises at least one of lithium, copper, silver, sodium,potassium, or magnesium.
 14. The solid state actuator of claim 12,wherein the solid state storage material comprises at least one of alithium storage material or MV₂O₅, where M comprises at least one of Na,Ag, Mg, K or Cu.
 15. The solid state actuator of claim 12, wherein theplating material is a material that is non-alloying with the cathodeelectrode.